This section provides background information which is not necessarily prior art to the inventive concepts associated with the present disclosure.
It is known to apply pinch sensors to prevent a power-activated window or closure panel, such as a lift gate or side door, from closing if a foreign obstacle or object is detected just as the panel closes. It is further known to apply a switch to an automotive seat to detect the presence of a passenger, which in turn can activate or deactivate an inflationary restraint apparatus, often referred to as airbag. The pinch sensors and switches come in different forms, including non-contact sensors such as those based on capacitance changes, and contact sensors which rely on a physical deformation of the sensor caused by contact with a foreign object.
The contact pinch sensors are typically applied in the form of a rubber strip which is routed along and adjacent to the periphery of a vehicle door. The rubber strip is conductive and embeds two small diameter conductive wires which are typically spaced from one another, often by an air gap. When the two wires are caused to contact one another under an impact force applied directly onto an outer, nonconductive sheath, typically a non-conductive elastomeric material, wherein the outer sheath encases the inner conductive rubber strip and conductive wires, the electrical resistance between the wires drops, and a microcontroller operably connected to the two wires detects the drop in resistance or voltage, thereby detecting an object when the resistance or voltage drop exceeds a predetermined threshold. Some fundamental problems result with such conventional pinch sensors are as follows, in no particular order of importance: they generally have a limited activation angle, typically on the order of about 35 degrees along each side, and thus, in the event the pinch force is applied obliquely rather than head on, the wires may not contact one another; they are generally complex and costly in construction, largely due to the need for complex extrusion process and crimping process used to fix a resistor to the ends of the wires, and further due to the need for over-molding of a non-conductive cover about the ends; and further yet, the routing of such pinch sensors can compromise the effectiveness of the sensor due to creating false activations via bending stresses and displacement of the wires.
It is further known to utilize motor Hall effect sensors, particularly in vehicle window applications. Hall effect sensors are typically costly to implement, and further, in vehicle window applications, it can prove challenging to meet the maximum force limitation allowable under vehicle standards imposed by the DEPARTMENT OF TRANSPORTATION (DOT), National Highway Traffic Safety Administration, 49 CFR Part 571, RIN 2127-AG36, Federal Motor Vehicle Safety Standards, Power-Operated Window (FMVSS), Partition, and Roof Panel Systems, under standard FMVSS 118, incorporated herein by reference. Difficulties in meeting the standard stem largely from a lag in time between the initial sensing of an object to the reaction time of stopping and/or reversing the window.
It is therefore desired to provide a sensor/switch that obviates or mitigates at least one of the above-identified disadvantages.